The first step was to cut one picket exactly 4
feet long. I made all the pickets from 12 foot long treated
1x6's, which gave a picket cost substantially less than using
8 foot boards.

Using the first picket as a guide, I fastened a
stop block to the workbench. I also fastened the miter saw to
the bench with lag screws.

My workbench here is a long scrap of OSB, just under 8 feet long
and less than 2 feet wide, screwed to a frame of 2x2's. I placed
that on the end of a utility trailer, which made an ideal working
height. But I also sometimes set the table-top on a pair of folding
sawhorses.

Clipping The Corners:

I carefully laid out cuts at 45 degree angles,
starting 1.25" in from the edges of the board.

I positioned the picket accurately and placed a
block of 2x4 against the end. I initially held the 2x4 in
place with a Quick-Grip clamp.

Then I cut through the picket and the stop
block. But the Quick-Grip clamp got in the way of the saw
handle, so I had to use a C-clamp instead. From here on it was
a simple matter of setting a picket against the saw fence,
sliding it up to the stop block, cutting it, then flipping the
board over to cut the other corner.

My high-volume production set-up
for cutting "dog-ear" corners:

A. Stack of square-cut pickets, 4' long.

B. Picket about to be cut.

C. Nearby stack of just-cut pickets.

D. Larger stack of finished pickets.

E. The stop block for cutting boards to length,
not used for this cutting operation.

If there's one thing I've learned from my education and
experience as an engineer, it's that some work "creates
value" and some work does not. In a fence project, like many
carpentry projects, value is created by cutting materials and
fastening them in their proper location. Marking boards, moving
lumber, laying out cuts, etc. do not create value. Hence, those
tasks must be eliminated or reduced in order to maximize
productivity. I had almost 200 cuts to make. If for each cut I took
10 seconds to align the saw blade with the line, that would be 33
minutes of moving wood around. Similarly, any time taken moving
boards from the "uncut" stack to the saw, then to the
"finished" stack, is time wasted. Such efforts add no
value. Keeping all materials close by means less time wasted.

In the above photo, I had the uncut pickets within reach of where
I stood. When cut, I placed them in a stack next to me, rather than
taking two steps to the larger stack. When I had cut a dozen
pickets, I moved the close-by stack to the sawhorses. I could have
put the saw horses closer to the saw, but it would have crowded the
scene for other work. My approach was a compromise.

Next I removed the miter saw and set up the
bench belt sander. I wanted to sand the cut edges of the
boards so they would be less likely to give someone a sliver.

The stack in the foreground is the pile of completed
pickets, ready for installation.

My procedure was to simply "roll" the
board with the end against the sanding belt. I sanded both top
and bottom of each board. The entire stack took about 45
minutes to complete.

The sanding creates a subtle rounded appearance
and is definitely worth doing if a bench mounted belt sander
is available.

The 4"x36" belt sander I used costs about $100 at
Sears. It comes in handy for smoothing out rough cuts and many other
tasks.